Is the result of modified Allen's test still accurate after endoscopic thoracic sympathectomy?

The radial artery (RA) is increasingly being used for coronary artery bypass grafting (CABG). Endoscopic thoracic sympathectomy (ETS) has been shown to block innervation of sympathetic nerves of upper limbs, which reduces sweating of hands and dilates blood vessels. The modified Allen's test (MAT) is one of the commonest methods of assessing collateral arm flow prior to RA harvest, though it has limitations. However, the reliability of MAT after ETS remains unclear. We therefore investigated the effects of ETS on the results of MAT.

A retrospective cohort study was conducted on 164 consecutive Chinese patients with palmar hyperhidrosis who underwent ETS between January 2016 and January 2019. The medical records were reviewed concerning the ultrasound examination and MAT results of their RAs and ulnar arteries (UAs) in both forearms before and after ETS.

The performance of ETS significantly increased the diameter of the right RA from 2.731±0.122 to 3.102±0.114 mm in men and from 2.347±0.074 to 2.915±0.162 mm in women. Similar effects of ETS were observed in expanding the diameters of the left RA and the UA. Meanwhile, there was no significant effect of ETS on systolic blood pressure (BP) and heart rate (HR). Overall, retesting of patients following ETS with a preoperative positive MAT result revealed a transition to a negative result.

ETS was effective in dilating RA in both men and women, which could lead to a false negative preoperative MAT result. Patients should be questioned about their history of ETS if their RAs are to be harvested for CABG. More studies are warranted to evaluate the safety of RA as a coronary artery graft after ETS.